CAPI: Rework controller state notifier

Another step towards proper locking: Rework the callback provided to
capidrv for controller state changes. This is so far attached to an
application, which would require us to hold the corresponding lock
across notification calls.

But there is no direct relation between a controller up/down event and
an application, so let's decouple them and provide a notifier call chain
for those events instead. This notifier chain is first of all used
internally. Here we request the highest priority to unsure that
housekeeping work is done before any other notifications. The chain is
exported via [un]register_capictr_notifier to our only user, capidrv, to
replace the racy and unfixable capi20_set_callback.

Signed-off-by: Jan Kiszka <jan.kiszka@web.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 12 deletions

diff --git a/include/linux/kernelcapi.h b/include/linux/kernelcapi.h
index a53e932f80fb..9c2683929fd3 100644
--- a/include/linux/kernelcapi.h
+++ b/include/linux/kernelcapi.h
@@ -48,9 +48,7 @@ typedef struct kcapi_carddef {
 #include <linux/list.h>
 #include <linux/skbuff.h>
 #include <linux/workqueue.h>
-
-#define KCI_CONTRUP     0       /* arg: struct capi_profile */
-#define KCI_CONTRDOWN   1       /* arg: NULL */
+#include <linux/notifier.h>
 
 struct capi20_appl {
         u16 applid;
@@ -67,11 +65,6 @@ struct capi20_appl {
         struct sk_buff_head recv_queue;
         struct work_struct recv_work;
         int release_in_progress;
-
-        /* ugly hack to allow for notification of added/removed
-         * controllers. The Right Way (tm) is known. XXX
-         */
-        void (*callback) (unsigned int cmd, __u32 contr, void *data);
 };
 
 u16 capi20_isinstalled(void);
@@ -84,11 +77,11 @@ u16 capi20_get_serial(u32 contr, u8 serial[CAPI_SERIAL_LEN]);
 u16 capi20_get_profile(u32 contr, struct capi_profile *profp);
 int capi20_manufacturer(unsigned int cmd, void __user *data);
 
-/* temporary hack XXX */
-void capi20_set_callback(struct capi20_appl *ap, 
-                         void (*callback) (unsigned int cmd, __u32 contr, void *data));
-
+#define CAPICTR_UP                      0
+#define CAPICTR_DOWN                    1
 
+int register_capictr_notifier(struct notifier_block *nb);
+int unregister_capictr_notifier(struct notifier_block *nb);
 
 #define CAPI_NOERROR                      0x0000